6-t-Butyl-2,3-xylenol and 6-t-butyl-3-cresol are useful as antioxidants.
6-t-Butyl-2,3-xylenol can be prepared by butylation of 2,3-xylenol with isobutylene using one of a variety of acidic catalysts such as sulfuric acid and boron trifluoride etherate. The selectivity to the desired product, however, is not particularly good due to the simultaneous production of 4-t-butyl-2,3-xylenol and 4,6-di-t-butyl-2,3-xylenol. The preceding statements apply also to the cresol homolog.
I have found a relatively straight-forward method of preparing 6-t-butyl-2,3-xylenol and 6-t-butyl-3-cresol. The method is also useful for preparing homologs of these materials wherein the methyl group is replaced by a C.sub.2 -C.sub.6 primary alkyl group.
The important features of my process are the use of a specific type of catalyst and a specific temperature range.